AC and Tachometer work while cranking then cut out.

[tg318is]

As the title says, while the engine is cranking and for a second after, the AC/fan runs and the tacho holds at idle for a second after the engine has cranked over then they both cut out at the same time. I thought it was my ignition switch so I replaced that (I was intending to anyway), but that wasn't the problem.

I have no when it comes to this stuff and tend to steer clear when it comes to electrical issues as I don't trust myself. I've no clue as to what it could be.

Also I have the standard temp/ fuel gauge don't work (I'm fairly sure that is my SI board)

EDIT: I forgot to mention my car had been sitting since Wednesday afternoon, when I went to start it this morning the battery had no charge. (3 week old battery)

[Gregs///M]

I would start by replacing the fuses for those circuits. Our cars, after a couple of decades, develop hairline cranks in the OEM fuses which can give intermittent power to those sources.

It is the cheapest, easiest way to begin your troubleshooting. I've seen many guys repair their cluster problems just by replacing fuses. Often a visual check is OK and sometimes even a multi meter will check out OK, but for old fuses, its best to use a test light or just replace.